1. Field of Invention
The invention relates to a flat panel display driver, and more particularly to a method for applying the same dithering table to different display panels.
2. Related Art
The development of the opto-electronic and semiconductor technology drives the flourishing development of the flat panel display. Among many flat panel displays, a liquid crystal display (LCD) has become the mainstream in the market because it has the superior properties, such as the high spatial utilization efficiency, the low power consumption, no radiation and the low electromagnetic interference. Thus, the LCD has been widely used in electronic products, such as the liquid crystal display of a notebook computer or a desktop computer and the display of a liquid crystal display television (LCD TV), relevant to the life. The driving circuit of the LCD panel is the key component, which influences the quality and the cost of the LCD.
FIG. 1 is a structure diagram showing a parallel matrix LCD panel according to the prior art. As shown in FIG. 1, the transversal red (R), green (G) and blue (B) sub-pixels are defined as one set in the structure of the LCD panel, and the previous row of red (R), green (G) and blue (B) sub-pixels is aligned with the next row of red (R), green (G) and blue (B) sub-pixels. The blue (B) sub-pixels in the first column are the unused pixels and are left when the panel is cut. FIG. 2 is a structure diagram showing a Delta matrix LCD panel according to the prior art. As shown in FIG. 2, the previous row of transversal red (R) sub-pixels and the next row of green (G) and blue (B) sub-pixels are defined as one set in the structure of the LCD panel. The previous transversal green (G) and blue (B) sub-pixels and the next row of red (R) sub-pixels are defined as one set. Th sub-pixels (R), (G) and (B) of each set of the sub-pixels are arranged to form the Delta, so the panel is also referred to as a Delta architecture panel. Similarly, the sub-pixels in the first column are the unused pixels and are left when the panel is cut.
In addition, the gray scale levels that can be displayed by the low-cost panel are only equal to 6 bits and are thus equal to 64 gray scale levels in the present driver of the LCD panel. So, the dithering algorithms are often used in the driver, wherein the dithering algorithms are divided into the time dithering algorithm and the spatial dithering algorithm. The spatial dithering algorithm is to simulate 256 gray scale levels using four pixels of 64 gray scale levels. For example, when the gray-scale data is 201, four pixels respectively display 50, 50, 50 and 51 to simulate the gray scale level, which has the brightness of 201 when being viewed by the human eyes. The time dithering algorithm is to divide the time into four sectors and to simulate the 256 gray scale levels using one pixel with 64 gray scale levels. For example, when the gray-scale data is 201, the gray scale levels of 50, 50, 50 and 51 are respectively displayed during the first time sector, the second time sector, the third time sector and the fourth time sector to simulate the gray scale level, which has the brightness of 201 when being viewed by the human eyes.
No matter which dithering algorithm is used, a dithering table is built in the LCD panel driver according to the present technology. Generally speaking, the dithering table is a M×N matrix having elements each serving as a dithering operator. In order to briefly describe the operating principle of the dithering table applied to the LCD panel driver, it is assumed that the dithering table is a 3×3 matrix and that the LCD panel to be driven is a parallel matrix LCD panel. When the LCD panel is to be driven, the first row of RGB sub-pixels is substituted into the first row of the dithering table, the second row of RGB sub-pixels is substituted into the second row of the dithering table, and the third row of RGB pixels is substituted into the third row of the dithering table. Next, the first row of second set of RGB sub-pixels is substituted into the first row of the dithering table, the second row of second set of RGB sub-pixels is substituted into the second row of the dithering table, the third row of second set of RGB sub-pixels is substituted into the third row of the dithering table, and so on. The color data is substituted into the dithering table according to the order of driving the pixels so that the driving values are obtained, and then the LCD panel is driven according to the driving values.
Next, as shown in FIGS. 1 and 2, the order of the dots of the even numbered scan lines on the Delta architecture panel is GBR, and the order of the dots of even numbered scan lines on the parallel matrix LCD panel is RGB. If the same dithering table is used according to the description mentioned hereinabove, the phenomenon that the even numbered scan lines are shifted by one dot occurs in the displayed effect. In order to make the phenomenon be more clearly understood, two examples will be described in the following.
FIG. 3 is a schematic illustration showing the pattern entropy, which is displayed after the display data of the conventional parallel matrix LCD panel is substituted into the dithering table and after the display data of the conventional Delta matrix LCD panel is substituted into the dithering table. As shown in FIG. 3, symbol 301 represents the pattern entropy distribution displayed when the display data of the parallel matrix LCD panel is substituted into the dithering table, and symbol 302 represents the pattern entropy distribution displayed when the display data of the Delta matrix LCD panel is substituted into the dithering table. As shown in FIG. 3, the dot data of the even numbered scan lines of the original parallel matrix LCD panel to be firstly dithered is red (R) pixel data, but the dot data of the even numbered scan lines of the original Delta matrix LCD panel to be firstly dithered is blue (B) pixel data. Thus, if two panels share the same dithering table, one of the display panels has the worse entropy distribution. In this example, it is found, from the displayed effect, that the entropy 302 on the right-hand side is worse than the entropy 301 on the left-hand side. In addition, the user sees the striped fine noise on the right displayed frame in practice.
FIG. 4 is a schematic illustration showing the pattern entropy, which is displayed after the conventional green display data of the conventional parallel matrix LCD panel is substituted into the dithering table and after the green display data of the conventional Delta matrix LCD panel is substituted into the dithering table. As shown in FIG. 4, when only the pure color, such as the green (G) color, is displayed, the nonuniform phenomenon of the entropy becomes more obvious on the Delta matrix LCD panel.
However, the economic effectiveness cannot be satisfied if the LCD panel driving circuit is modified only for the purpose of the applications to different panels. Thus, it is necessary to provide the method for applying the same dithering table to different display panels and the method for sharing the same dithering table.